• It is a science which concerns with the occurrence, distribution and movement of water.
  • It may also be define the science that deals with the depletion and replenishment of water sources.
  • When we say movement of water, it includes movement of water in atmosphere, on the surface of the earth, and below the surface of the earth.
  • In atmosphere, water is present in form of vapours. On surface of earth it is in form of rivers, lakes, ponds and snow etc.
  • Below the earth surface it is present in form of moist soils.
  • The water occurring below the surface of the earth is known as ground water.
  • Ground water occupies the voids of the soil.

Hydrological Cycle.

  • Except for the deep ground water, the total water supply of the earth remains in constant circulation between earth and atmosphere.
  • This water again falls over the earth in form of precipitation.
  • The part of precipitation again evaporates back to atmosphere, part is soake by the ground.
  • Rivers again join the oceans and evaporation of water again occurs from them.
  • The water that has percolated in to the ground either joins oceans or is brought to the surface by means of wells, infiltration gallerries etc.
  • So circulation of water from earth to atmosphere and back to earth is a continuous process.
  • It is this circulation of water or hydrological cycle, which keeps on using and then replenishing water.


  • By measuring the elements of